One of the main characteristics of excavator pressure transmission compared with other transmissions is that more types and numbers of valves are used to control the direction, flow and pressure of the fluid flow, so as to realize the action requirements of hydraulic machinery under different operating conditions. Many, according to their role in the hydraulic system, can be divided into the following categories
1, pressure control valve
is used to control or adjust the hydraulic pressure valve in the hydraulic system, such as safety valve, relief valve, back pressure valve, etc.
2, flow control valve
Maintain the liquid flow rate at a certain value to adjust the movement speed of the working mechanism, such as throttle valve, stroke control wide
3, direction control valve
is used to control the direction of the liquid flow. There are two kinds of reversing valve and one-way valve. The reversing valve is divided into two kinds of spool valve and rotary valve.
In the hydraulic excavator, the most used is the reversing valve (also known as the control valve). Reversing is often used to directly control the movement direction of each working mechanism of the hydraulic baler. In order to reduce the installation volume of the reversing valve and facilitate the connection of the oil circuit, several reversing valves and safety valves are often bolted together, or the valve body is made into a whole, which is called a multi-way reversing valve group, also known as Multi-way combination valve.
valve type reversing valve has good sealing performance and sensitive action, but the force required to open the valve is relatively large, so it is rarely used.
Rotary valve type switching valve relies on the spool to rotate in the valve body to change the liquid flow direction. Due to the unbalanced radial force, the sealing performance is poor, and it is mostly used for low pressure winding.
Slide valve type reversing valve controls the direction of liquid flow by moving the valve stem in the valve body, and is the most widely used on hydraulic excavators. The number of spool valve positions is determined by the number of working positions of the valve stem in the valve body. It is represented by the number of squares in the system diagram, which can be divided into two positions, three positions and multiple positions. The number of oil inlets and outlets of the main oil circuit on the spool valve body is called the number of passes. Generally, the middle square of a three-position valve represents the middle position of the valve. The path form when the spool valve is in the middle position is called the function of the spool valve. For example, the spool valve has O type, H type, M type and so on.
In order to facilitate the design and production of valves to achieve standardization and serialization, valves of the same structure are often used, and valve stems of different structures are used to obtain valves with different functions. Because the production of the valve body is more complicated, adopting the above-mentioned method will facilitate the mass production of the valve body.
